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General Description

Herring have a blue-green upper body with silvery sides and are devoid of markings. The body is laterally compressed and the scales along the underside project in a slightly serrated arrangement. Scales are large and easily removed. Their tails are deeply forked and they lack adipose fins. These fish may grow to 18 inches in length, but a 9-inch specimen is considered large.

Their blue-green upper body, large scales, and large eyes help distinguish them from other silver fish species of similar size.

Life History

Growth and Reproduction

Pacific herring are sexually mature at 3–4 years of age and spawn every year after reaching maturity. Spawning occurs in
the spring in shallow, vegetated areas in intertidal and subtidal zones. Males and females release their milt and eggs into the
water column where they mix and fertilize. The eggs are adhesive and attach to vegetation or the bottom substrate.

Eggs hatch about two weeks after fertilization and the young larvae drift and swim in the ocean currents. Once the larvae undergo
metamorphosis into their juvenile stage, they rear in sheltered bays and inlets. In the fall, the schools of juveniles move to
deeper water where they will spend the next 2-3 years. They will remain separate from the adult population until they are mature.

Feeding Ecology

Pacific herring feed seasonally on phytoplankton and zooplankton, building up fat stores for periods of inactivity. They generally
feed in surface waters at night in areas of upwelling. Young herring feed mainly on crustaceans but will eat decapods and mollusk
larvae. Adults consume mostly large crustaceans and small fish.

Behavior

Pacific herring travel in large schools.

Migration

Pacific herring travel to inshore waters to spawn then migrate back to offshore waters to feed. They exhibit a diel vertical
migration pattern, remaining near the bottom during the daylight hours and moving to shallow waters to feed at night.

Range and Habitat

Pacific herring are found throughout coastal waters of the Pacific Ocean. In the western North Pacific, they are found in
the western Bering Sea to Kamchatka, in the Okhotsk Sea, and around Hokkaido, Japan southeast to the Yellow Sea. In the
eastern North Pacific, they range from Baja California north to the Beaufort Sea. They also occur in the Russian Arctic
from the Chukchi Sea to the White Sea.

Pacific herring spawn in inshore waters and feed in offshore waters. They occupy the water column from the surface to
depths of 1300 feet.

Status, Trends, and Threats

Status

Herring population abundance trends are very dynamic and are subject to fairly substantial changes on both large and small geographic scales. The primary cause for such fluctuations in abundance is environmental change that affects herring growth and recruitment.

Trends

Overall, Alaska herring stocks are well managed for their long-term sustained yield. In Southeast Alaska, herring abundance
is trending upwards since 1980. The Pacific herring population in Prince William Sound collapsed in 1993, 4 years after the Exxon Valdez oil spill. The cause has yet to be determined and the population has shown little sign of recovery.

Threats

A threat to Pacific herring is the loss of spawning grounds. This habitat has been degraded or destroyed by dredging, construction activities, log storage, oil spills, and decreases in water quality. Global warming may also pose a threat to the species by reducing the availability of their prey; zooplankton and phytoplankton. In addition, the recovery of populations of predator species, such as humpback whales, may impact herring populations.